how do i make this work, does not work like a normal list. I have to delete from the list, which contains i.

if my list contains (2,4,3,13,21,14,15,30)

I want to delete the first 6 elemtent.

  Public randomcards As New HashSet(Of Integer)

        For i As Integer = 0 To 5
          randomcards.remove(i)
        Next

so after the operation, my list will become 15,30 with only 2 element.

Unfortunately, this is not a normal list and I would need a little help

CodePudding user response：

By definition, an HashSet collection is not sorted (see the documentation), so

I want to delete the first 6 element

makes no sense.

If you know which element you want to remove (for example the number 14), use

randomcards.Remove(14)

By the same principle, if you want to remove 6 randomic integer (compliance with the insertion order is not guaranteed!), you can do something like this:

Dim fakeList As Integer() = randomcards.ToArray()
For i As Integer = 0 To 5
    randomcards.Remove(fakeList(i))
Next

CodePudding user response：

This is rather tedious because you can't refer to items in a HashSet by index. Keep in mind you can't alter any collection in a For Each by removing an element.

1. Create a HashSet.

2. Create a list.

3. Add the first 6 elements of the HashSet to the list.

4. Loop through the list checking if the item in the list is in the HashSet. If True remove it.

   Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
       Dim hs As New HashSet(Of Integer) From {2, 4, 3, 13, 21, 14, 15, 30}
       Dim lst As New List(Of Integer)
       Dim counter As Integer
       For Each i In hs
           If counter < 6 Then
               lst.Add(i)
           Else
               Exit For
           End If
           counter  = 1
       Next
       For Each i In lst
           If hs.Contains(i) Then
               hs.Remove(i)
           End If
       Next
       MessageBox.Show(hs.Count.ToString)
       For Each i In hs
           Debug.Print(i.ToString)
       Next
   End Sub
   

@Calaf's answer look superior.